SIR measurement is an important technology in a CDMA mobile communication system, and is mainly used in power control, soft hand-over and cells search etc. The SIR measurement provides real time and effective signal-to-interference ratio information for normal operation of a system. Performance of a mobile communication system is directly affected by measurement accuracy of the SIR. Conventional SIR measurement can refer to article “SIR-Based Transmit Power Control of Reverse Link for Coherent DS-CDMA Mobile Radio” (IEICE TRANS. COMMUN. VOL. E81-B, NO. 7 JULY 1998). With reference to FIG. 1, the SIR measurement procedure can be summarized as following:
1) After passing through RAKE combiner 1 of the RAKE receiver, a transmitted multipath signal is formed a single-path signal.
2) The combined RAKE signal is sent, on the one hand, to the signal power measurement-device 2 for signal power estimate, and on the other hand, to the interference power measurement-device 3 for interference power estimate. The formulas for estimate can refer to the above document.
3) The output of the signal power measurement-device 2 and interference power measurement-device 3 is divided by the divider 4 to obtain the SIR measurement value.
The conventional SIR measurement method measures SIR with the single-path signal after RAKE combining at receiving end. Nevertheless, the signal is transmitted with multipath and is received by multipath receiving technology at receiving end. Therefore, the interference measurement is unrealistic and part of the interference result is lost. Moreover, since a channel of the mobile communication system is a Rayleigh-fading channel; when the channel is at heavy fading depth, the conventional SIR measurement method cannot really reflect channel variation and cannot provide to the system accuracy and effective information.